diff --git a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2TemplateTests.java b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2TemplateTests.java
index 7c44be0b953..31e3a6fa056 100644
--- a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2TemplateTests.java
+++ b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2TemplateTests.java
@@ -8047,6 +8047,17 @@ public class AST2TemplateTests extends AST2TestBase {
 		parseAndCheckBindings();
 	}
 	
+	//	template <typename... Args>
+	//	void waldo(Args...);
+	//
+	//	int main() {
+	//	    waldo<int>();
+	//	}
+	public void testExplicitArgumentsForParameterPack_404245() throws Exception {
+		BindingAssertionHelper helper = getAssertionHelper();
+		helper.assertProblem("waldo<int>()", "waldo<int>");
+	}
+
 	//	template <typename T>
 	//	struct A {};
 	//
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPFunction.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPFunction.java
index 12a5d5c201a..0ad6f654d7d 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPFunction.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPFunction.java
@@ -654,7 +654,10 @@ public class CPPFunction extends PlatformObject implements ICPPFunction, ICPPInt
 
 	@Override
 	public boolean hasParameterPack() {
-		ICPPParameter[] pars= getParameters();
+		return hasParameterPack(getParameters());
+	}
+	
+	public static boolean hasParameterPack(ICPPParameter[] pars) {
 		return pars.length > 0 && pars[pars.length - 1].isParameterPack();
 	}
 
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPFunctionSpecialization.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPFunctionSpecialization.java
index d2e1f13c2ae..72e6cfadb14 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPFunctionSpecialization.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPFunctionSpecialization.java
@@ -69,12 +69,12 @@ public class CPPFunctionSpecialization extends CPPSpecialization implements ICPP
 
 	@Override
 	public int getRequiredArgumentCount() {
-		return ((ICPPFunction) getSpecializedBinding()).getRequiredArgumentCount();
+		return CPPFunction.getRequiredArgumentCount(getParameters());
 	}
 
 	@Override
 	public boolean hasParameterPack() {
-		return ((ICPPFunction) getSpecializedBinding()).hasParameterPack();
+		return CPPFunction.hasParameterPack(getParameters());
 	}
 
 	@Override
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPTemplates.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPTemplates.java
index f05489611ab..71ceff23b34 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPTemplates.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPTemplates.java
@@ -2041,8 +2041,17 @@ public class CPPTemplates {
 				IBinding instance= instantiateFunctionTemplate(template, args, map, point);
 				if (instance instanceof ICPPFunction) {
 					final ICPPFunction f = (ICPPFunction) instance;
-					if (SemanticUtil.isValidType(f.getType()))
-						return f;
+					if (SemanticUtil.isValidType(f.getType())) {
+						// The number of arguments have been checked against the function
+						// template's required argument count at an earlier stage. However,
+						// the process of instantiation can increase the required argument
+						// count by expanding parameter packs. If arguments are provided
+						// for a parameter pack explicitly, it's possible for deduction to
+						// succeed without having enough function arguments to match a 
+						// corresponding function parameter pack - so we check again.
+						if (fnArgs.size() >= f.getRequiredArgumentCount())
+							return f;
+					}
 				}
 			}
 		} catch (DOMException e) {